Human saliva is supersaturated with respect to the calcium phosphate salts which form dental enamel, a condition which would normally generate unwanted and potentially harmful precipitation of calcium phosphate salts in the salivary glands and on the teeth. These, undesirable side effects are prevented by 2 salivary phosphoprotein, statherin and the acidic proline-rich proteins (PRP), which are potent inhibitors of calcium phosphate precipitation. Because of their activities, saliva provides a prospective, reparative but stable environment which is important for maintaining the health of the teeth. Our objectives are to gain a sound understanding of these protective and reparative functions, to relate them to oral health and disease, and to achieve a level of knowledge which will help to ensure that these natural oral defense mechanisms fully express themselves in the mouth. Previous studies by the applicant and co-investigators led to the identification of statherin and the PRP's as inhibitors of calcium phosphate precipitation, made a major contribution to the determination of their structures, and made substantial advances towards establishing the molecular mechanisms by which these unusual macromolecule act. It is now proposed to advance understanding of these functions and mechanisms of action of these molecules in the following ways: 1) by synthesizing phosphoserine- containing peptide analogs of statherin and the PRP's for structure studies b) by investigating mechanisms of post-translational phosphorylation of statherin and the PRP's by using serine- containing peptide analogs specifically synthesized for this purpose, 3) by studying analogs of statherin and the PRP's from nonhuman mammals to gain further insights into structure-function relationships and evolutionary aspects of these molecules, and 4) by studying specific aspects of the behavior and fate of statherin and the PRP's in the oral cavity, an important site at which they act but where they are subject to degradation by oral microflora. The work will be advanced by use of modern gas-phase microsequencing methods and solid phase peptide synthesis techniques. From this work will come advances in understanding of an important tooth-protective system and new knowledge of the modulation of the chemistry of calcium phosphates by specific and unusual phosphoprotein.